The present invention relates to conveyor apparatus including a stop and, in particular, to such apparatus useful in palletizers.
A palletizer is a mechanism which automatically arranges incoming cartons or other objects, hereinafter generally termed "cartons" for purposes of simplicity, into rows which are then formed into tiers or layers. The formed tiers are subsequently deposited successively onto a pallet which, when fully loaded, is moved from the mechanism by a fork-lift truck or the like for storage or shipping.
Palletizers are manufactured in a variety of different forms, but, in general, may comprise a carton orienting means, a row forming means, a layer or tier forming means, an elevator or hoist located below the draw plate upon which the formed layers or tiers are successively deposited, and a means for conveying empty pallets to the elevator or hoist and for removing loaded pallets from the elevator or hoist.
Preferably the carton orienting means includes a carton inverter and a means for turning the carton through a 90.degree. angle. Adjustable pattern guides and stops may also be provided. In fully automatic palletizers, the functions of the various portions of the mechanism are synchronized and controlled by a main control unit which may be programmable through the use of tape or other program media. By controlling the carton inverter, the means for turning the carton 90.degree., the row forming means with its stops and guides, and the tier forming means, a large variety of different load patterns can be achieved to provide the load stability and degree of compactness required by the particular size or shape and weight of the cartons involved.
In order to achieve a large variety of different load patterns automatically, it is necessary that the palletizer, and particularly the row forming means and the tier forming means, be quite versatile in operation. Versatility in forming different patterns is achieved by developing the capability to individually orient each carton in the pattern and also by the maintaining of gaps or spaces between adjacent cartons in a row as well as between cartons in adjacent rows.
It is relatively easy to establish a gap or space between adjacent cartons in a row. Many conventional row forming means comprise a roller table comprising a plurality of parallel oriented, spaced, copolanar rollers. The rollers are driven by a motor or the like which is actuated by the control unit in accordance with the program. Incoming cartons, after they are appropriately oriented, enter one side of the row forming table and are conveyed by the rollers towards an end stop at the other side of the table. If a gap or opening is required, a stop is provided at the appropriate location along the table in the form of a plate which is movable between two adjacent rollers from below the surface of the rollers to a position above the surface of the rollers. In its raised position, this stop prevents a carton from progressing any further along the table and thus serves to maintain a space or gap between the cartons, in the desired location, as the remainder of the cartons enter the row forming table. Thus, through the use of several strategically located stops, a row of cartons may be formed with spaces or gaps between adjacent cartons.
The stops utilized to form the spaces or gaps between adjacent cartons in a row may be actuated in any appropriate manner, such as by pneumatic or hydraulic cylinders. The control unit functions to synchronize the actuation of the stops. In this manner, the program is utilized to control the formation of the gaps or openings between adjacent cartons in the row. Thus, the formation of the openings or gaps between the adjacent cartons is variable to produce a variety of different row patterns.
After the row is formed on the row forming table, it is swept from the row forming table to a tier forming table. The tier forming table may comprise a plurality of driver rollers similar to those of the row forming table. Normally these rollers are oriented perpendicular to the rollers of the row forming table to permit the formed row to be swept from the row forming table in a direction perpendicular to the movement of the cartons on the row forming table, thereby maintaining the spaces or gaps therein.
As each row is received on the tier forming table, from the row forming table, the rollers of the tier forming table are driven to advance that row to the opposite end of the table. Thus, the first row received on the tier forming table is advanced until it is adjacent an end stop on the opposite end of the tier forming table. When the next row is received, the rollers are again driven such that this row is advanced against the first row. In this manner, each successive row is advanced by the movement of the rollers until it is adjacent the previous row.
As the formed rows of cartons are being swept from the row forming table to the tier forming table, the leading edge of some cartons may extend further than the leading edge of other cartons, either because the cartons are of a different size or because some cartons were reoriented (i.e., acted on by the means for turning the carton 90.degree.) and others were not. In some instances, although not all, it may be desirable to align the leading edges of all the cartons of a given row as part of the tier forming process. For this purpose, the tier forming table may also be provided with one or more raisable stops essentially similar to those of the row forming table, but effective to provide an abutting surface for the leading carton edges so that, as the cartons of a given row are driven against the raised stop, the advanced leading edges are restrained until the lagging leading edges catch up.
The raisable stops, whether used on the row or tier table, contain upwardly projecting plate portions (called article stops or stop plates) which must be thin enough to pass between adjcacent rollers, yet strong enough to stop the forward motion of the cartons. Depending upon the speed with which the cartons impinging upon the stop plate are travelling, and the weight of the cartons (including their contents), the cartons may be possessed of considerable momentum at the time they strike the stop plate. In extreme cases the impact may have the result of injuring the carton (that is, crumpling the forward edge of the carton which impinges upon the stop), damaging any fragile contents of the carton (for example, bottles or glassware), and deforming the stop plate to the point of non-functionality (for example, by ending it so far forward toward the adjacent upstream roller that the stop plate is either no longer movable to a retracted position or simply tilted so much that the leading edge of the next carton to hit the stop plate may tend to ride up the stop plate or even go over the stop plate).
Accordingly, it is an object of the present invention to provide a stop which is effective to reduce the momentum with which a carton impinges on the stop plate.
It is another object to provide such a stop which reduces the danger of damage to the carton and/or its contents as well as to the stop plate itself.
It is also an object to provide such a stop which is of relatively simple and rugged construction.